Epoxy tape

ABSTRACT

An epoxy tape useful as an adhesive sealant comprised of a first band of an uncured epoxy resin composition and a second band comprised of a composition capable of curing the epoxy resin. Kneading together of substantially equal lengths of opposed portions of the first and second bands results in an epoxy composition which is self-curing.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part application of my copendingapplication Ser. No. 141,664, filed May 10, 1971, for an ElastomericTape, now U.S. Pat. No. 3,708,379.

Various epoxy resin compositions useful as adhesive sealants areavailable commercially. These compositions generally comprise uncuredepoxy resins together with curing agents therefor. Curing is effected bythe addition of the curing agent to the epoxy resin.

Since the epoxy resin and curing agent cannot be combined prior to thetime of use, otherwise premature curing occurs, it is customary tosupply the epoxy resin in a package separate from that of the curingagent. In use, the contents of the two packages, frequently tube-likecontainers, or portions thereof, are combined to provide a self-curingepoxy resin composition. Such systems are undesirable from thestandpoint of packaging costs and ease of use. In addition, the customeris required to follow specific mixing instructions if he is to obtainsatisfactory adhesive sealants.

It is the object of this invention to provide a room temperature,self-curing epoxy resin composition in tape form. A further object ofthis invention is to provide a room temperature self-curing epoxy resinuseful as an adhesive sealant in tape form. Another object of thisinvention is to provide an epoxy resin composition containing both anepoxy resin and a curing system therefor which requires no specialpackaging or storing conditions, yet remains in a stable, uncured statefor an indefinite period of time and is readily curable by simple mixingby either hand or machine to form an epoxy adhesive sealant havinguseful chemical and physical properties. Yet another object of thisinvention is to provide an epoxy composition in tape form such that anyportion thereof contains the proper proportion of epoxy resin and curingagent therefor.

DETAILED DESCRIPTION OF THE INVENTION

According to this invention, the above-described objects and advantagesare obtained by preparing an epoxy tape comprising a first band of anuncured epoxy resin composition and a second band, said bands beingjoined in close side-by-side relation throughout their entire lengths,said second band comprising a composition capable of curing said epoxyresin in said first band when said first and second bands are combinedto form a substantially uniform mixture.

In the appended drawings, FIGS. 1 through 4 are plan views illustratingvarious embodiments of the epoxy tape of this invention. The variousembodiments illustrated in the drawings are discussed in further detailhereinafter.

The epoxy tape of this invention has two principal components, viz., anuncured epoxy resin and a curing system for the epoxy resin. The epoxyresins which may be employed are complex polymeric reaction products ofpolyhydric phenols with polyfunctional halohydrins. Such resins areavailable commercially and are typically the product of a reactionbetween epichlorohydrin and 2,2-bis(p-hydroxyphenol) propane (BisphenolA). By adjusting the ratio of Bisphenol A to epichlorohydrin, epoxyresins of different physical properties are obtained. For example,resins made with a low Bisphenol A to epichlorohydrin ratio generallyare characterized by a high viscosity.

Epoxy resins are also characterized by their oxirane oxygen content andtheir epoxy equivalent weight, the epoxy equivalent weight being themolecular weight of the resin divided by the mean number of oxiraneoxygen rings per molecule. The epoxy resin compositions utilized toprepare the adhesive sealants of the present invention include semisolidepoxy resins, solid epoxy resins, liquid epoxy resins and mixtures ofthe above resins in proportions such that when admixed with suitablefillers, pigments and the like, a putty-like composition which can beextruded into tape form is prepared.

The curing system for the uncured epoxy resin will generally compriseany of the well known curing agents for epoxy resins such as a resinouspolyamide composition. As will be discussed in more detail hereinafter,specific curing agents utilized in a given epoxy tape composition willdepend primarily on the specific epoxy resin utilized in forming thetape and to a lesser extent on the rate and degree of curing desired forthe epoxy tape. Thus, the resinous polyamide utilized as a curing agentfor the epoxy resin may be selected from the group consisting of asingle polyamide, or a blend of two or more polyamides. Polyamide resinsare condensation products of polymerized fatty acids with polyalkylpolyamines prepared according to procedures well know in the art.

In addition to the uncured epoxy and the curing system components, theepoxy tape may contain a variety of conventional and special purposeingredients. Thus, the uncured epoxy and curing system components may becombined with various fillers, plasticizers, colorants and the like toprovide compositions having the physical properties required for forminga tape.

The fillers and other components must be selected and combined with theepoxy resin or curing agent in such a manner as to provide compositionswhich can be formed into the desired tape by extrusion. To accomplishthis, the material making up each band of the tape is formulated into a"putty-like" composition, and the respective compositions aresimultaneously extruded in side-by-side relationship to produce a lengthof tape. Moreover, the tape should be so formulated that little, if any,migration or interaction occurs between the curing system component inone band of the tape and the epoxy resin in the other band. That is, theepoxy tape is formulated so that the epoxy resin and the curing systemcomponents therefor are contained in separate bands making up the tapein such a manner that the epoxy resin itself will not cure untilsubstantially equal lengths of the respective bands are combined into asubstantially uniform mixture, after which curing proceeds as inconventional epoxy compositions.

Considering the invention in greater detail in connection with thedrawings, it is noted that the epoxy tape may be prepared in variousforms.

FIG. 1 illustrates an epoxy tape in which band 1 contains the epoxyresin composition and band 2 contains a polyamide resin compositioncapable of curing said epoxy resin.

FIG. 2 illustrates an epoxy tape in which the composition of therespective bands is that described with respect to FIG. 1, however, thebands of tape are superimposed in their greater dimension one on theother throughout their length.

FIG. 3 illustrates an epoxy tape in which band 1 of the tape containsthe epoxy resin composition while band 2 of the tape contains a curingagent for the epoxy resin. Between bands 1 and 2 is band 3, a neutralband which does not contain either the epoxy resin or a curing agenttherefor but rather is a band of the various non-reactive componentsincluding plasticizers and fillers which may be useful in forming theepoxy tape, the three bands being in side-by-side relationshipthroughout their lengths with band 3 acting as a physical barrierbetween bands 1 and 2.

FIG. 4 illustrates another form in which the tape of this invention maybe constructed. In this embodiment, for example, band 1 contains anepoxy resin while band 2 contains a curing agent for the epoxy resinmuch in the same manner as described for the tapes illustrated in FIGS.1 through 3 above. It is desirable to prepare tapes in the form shown inFIG. 4 when one of the materials making up a band of the tape is notstable on contact with air or does not have sufficient cohesiveness tobe self-supporting.

To prepare the elastomeric tape illustrated in FIG. 1, two separateputty-like masses are formed, one containing the epoxy resin admixedwith fillers, plasticizers, colorants and the like and the othercontaining a curing system for the epoxy resin also admixed withfillers, plasticizers, colorants and the like. Each putty-like mass isthen extruded through a co-extrusion die to form the desired tape. Epoxyresins desirable for use in the present invention include solid epoxyresins having an epoxy equivalent weight of about 385 to about 500 and amelting point of from about 60 to 75° C.; liquid epoxy resins having anepoxy equivalent weight ranging from about 185 to about 200 and aviscosity ranging from about 120 to about 160 poises at 25° C.; andsemisolid epoxy resins having an epoxy equivalent weight ranging fromabout 650 to about 750 and a kinematic viscosity (viscosity of asolution containing 75%, by weight, of the epoxy resin in xylene), of 15to 25 poises at 25° C. Mixtures of said resins having a kinematicviscosity ranging from about 0.01 to about 10 poises at 25° C. such asare formed when from about 50 parts to about 300 parts of a solid epoxyresin such as that described above are combined with about 100 parts ofa liquid epoxy resin such as that defined above, may also be utilized.

A desirable curing system for the epoxy resin comprises a semisolidresinous polyamide having a viscosity of about 5 to about 80, preferablyabout 10 poises at 150° C. and an amine value ranging from 85 to 95.Resins of this type are available commercially as Versamid® of GeneralMills. Mixtures of this polyamide resin with lower viscosity and morereactive resins such as those having a viscosity of about 5 to about100; preferably about 35 poises at 75° C. and an amine value rangingfrom about 230 to about 380 may also be utilized. Resins of this typeare also available commercially under the trademark Versamid fromGeneral Mills. In general, a blend of polyamide resins utilized in thetape of the invention should have an amine value ranging from 90 to 375and a viscosity of 5 to 80 poises at 150° C.

To accomplish satisfactory curing of the epoxy resin, there should be asufficient amount of the curing agent in the curing system to crosslinkat least about 70 to about 150% preferably about 100% of the availablecrosslinking sites in the epoxy resin in the tape. Curing to this extentcan be achieved with the use of from about 40 to about 150 preferablyabout 100 parts of a polyamide curing agent per 100 parts of epoxy resinin the tape.

The epoxy resin and the polyamide resin curing agents therefor areadmixed with various fillers, colorants and plasticizers to form therespective putty-like compositions which are extruded into the epoxytape of this invention. Useful fillers include talc, powdered aluminaand asbestos fiber. Fillers such as these provide the epoxy resin andthe polyamide resin compositions with the physical properties necessaryfor extrusion into tape form and also enhance the properties of thecured system. The fillers are incorporated into the epoxy resin andpolyamide resin compositions in amounts sufficient to produce aputty-like mass which can be easily extruded into the desired epoxytape. Finely powdered talc such as Mistron Vapor® of the United SierraDivision of Cypress Mines Corporation is an especially preferred filler,since it yields a handleable putty-like mass with both epoxy resins andpolyamide resins. The putty-like masses compared with this filler showless tendency to stick to the hands than do putty-like masses comparedwith other fillers. Plasticizers include resinous polyols and otheragents which serve to soften the cured epoxy tape.

Colorants may be included in the epoxy or curing agent compositions asdesired. Useful colorants include pigments like titanium dioxide whichprovides a white color; carbon black for black color and various organicand inorganic pigments for other colors. It is desirable that therespective bands of the epoxy tape be of contrasting color to facilitateuse of the epoxy tape.

In use, a portion of the tape comprising substantially equal lengths ofeach band of the tape is selected and the bands are mixed together, e.g.by hand. The mixing permits the components of the polyamide curingsystem to react with the epoxy resin composition effecting curing, insitu. When the bands of the tape are of contrasting color, it is easy todetermine when a uniform mixture has been obtained simply by continuingmixing until the mixture has a uniform color. It will be appreciatedthat pigment may be included in one or both bands of the elastomerictape.

The epoxy tapes illustrated in FIGS. 1 and 2 may be prepared in thefollowing manner. The composition comprising each band of the tape isprepared separately by mixing together of the constituents, and theseparate mixtures are extruded through a co-extrusion die. In preparingthe epoxy and polyamide compositions for extrusion, the dry ingredientsare combined with the liquid or liquified epoxy or polyamide resins toform highly viscous, smooth, putty-like masses. The separatecompositions are then formed into cylindrical slugs which can beintroduced to a suitable extruder. The compositions forming therespective bands are extruded from twin extruders arranged at rightangles to one another and the extrudates are then co-extruded through adie which simultaneously lays down the respective bands in side-by-siderelationship to form a tape. The tape is generally extruded onto amoving strip of a release paper such as parchment paper or siliconerelease paper. The release paper moves at a constant rate on an endlessbelt and is controlled so that the extruded tape is not pulled orallowed to buckle. The bands of the material being extruded through theco-extrusion die may have different rheological properties at any giventemperature, which causes the materials to pass through the die atdifferent rates. To alleviate the problem and to insure that the bandsare extruded at substantially the same rate, the material which extrudesmore slowly should be maintained at a higher temperature than that ofthe other extrudate. During the extrusion process, the temperature ofboth compositions should not exceed about 150° F., otherwise prematurecuring of the epoxy at the interface between the bands may result.

To prepare the tape illustrated in FIG. 3, the constituents of each bandare prepared as described above; however, that are, of course, threeseparate putty-like compositions for the extrusion process. Thecompositions forming the three bands are extruded from three extrudersleading to a single tri-extrusion die which simultaneously lays downthree bands in side-by-side relationship to form the tape of FIG. 3.

After extrusion, any desired length of the tape may be simply rolled upand packaged in any desired manner. There is no need for specialpackaging requirements to give a useful shelf life to the tape.

In use, any desired quantity of the epoxy tape made up to equal lengthsof each band in the tape are selected and kneaded together under ambientconditions forming a uniform mixture. The resulting dough-like epoxymaterial has a useable pot life of approximately 4 hours and will fullycure to a useful tough, solid epoxy adhesive in about 24 hours. Theepoxy resin formed from the epoxy tape of this invention has excellentadhesive sealant properties and may be utilized to adhere ceramic, woodand metal and like materials, to aluminum, concrete, steel, ceramic andlike substrates. The epoxy composition will cure at ambient temperature;however, curing will be accelerated at elevated temperatures. Forexample, the epoxy composition will cure completely in about one hour'stime if heated to a temperature of about 200° F. Moreover, the epoxycomposition will cure underwater making it useful in many marineenvironments.

It is known that electrically conductive carbon black may beincorporated into various substances to increase the electricalconductivity thereof. The epoxy tape of this invention may includeelectrically conductive carbon black such as Vulcan X-C 72 from CabotCorporation in amounts sufficient to impart at least semiconductiveproperties to the cured epoxy composition formed from the tape. This maybe accomplished by incorporating a total of about 30%, by weight, basedon the weight of the epoxy tape of electrically conductive carbon blackin the tape. The electrically conductive carbon black may beincorporated in one, or both, bands of the epoxy tape in any proportion.Even more highly conductive epoxy compositions can be formulated byincorporating about 40%, by weight, based on the weight of the epoxytape, of finely-divided silver powder in the epoxy tape.

The following examples are set forth as illustrative of the presentinvention:

EXAMPLE 1

19 parts of a liquid epoxy resin having an epoxy equivalent weight of185 to 196 and a viscosity of 120 to 160 poises at 25° C. is combinedwith 27 parts of a solid epoxy resin having an epoxy equivalent weightof 385 to 500 and a melting point of 60° to 75° C. in a steam jacketed,double arm, sigma blade mixer. The resins are mixed until a uniformviscous solution is achieved and 44 parts of powdered talc, (MistronVapor® by United Sierra Division of Cypress Mines Corporation) is addedand mixed slowly with constant agitation forming a highly viscous,smooth material. During this mixing procedure, the mixture should becooled so that the temperature of the mass does not exceed 120° F. Asecond mixture is prepared by mixing 57 parts of a semisolid polyamideresin having an amine value of 90 and a viscosity of 10 poises at 150°C., (Versamid® 100 of General Mills) with 43 parts of powdered talc,(Mistron Vapor®), in a sigma blade mixer maintained at a temperature notexceeding 120° F. until a uniform mixture is formed.

Equal portions, by weight, of each mixture are formed into slugs and fedseparately into twin extruders positioned at right angles to oneanother, the extruders feeding each mass into a co-extrusion die whichsimultaneously lays down a band of each mixture in side-by-siderelationship onto a moving strip of parchment release paper (Patapar® 40of Paterson Parchment Company). The release paper moves over an endlessbelt at a constant rate so that the extruded bands are not pulled orallowed to buckle. To insure the bands are extruded at substantially thesame rate, the material which extrudes more slowly is maintained at ahigher temperature than that of the other, however, in no event shouldthe temperature of either mixture exceed 150° F.

As the bands of each material are laid down in side-by-side relationshipa tape is formed which is rolled into any convenient length and packagedas any conventional tape. To utilize the tape, any length thereof isremoved from the roll, separated from the release paper and kneaded byhand or machine until a uniformly colored mixture is obtained. Themixture may be utilized as a metal to metal adhesive sealant which whenallowed to stand while curing occurs forms a tough, hard adhesive seal.

EXAMPLE 2

Following the procedure and utilizing the apparatus described in Example1, two separate mixtures are prepared as follows: 100 parts of asemisolid epoxy resin (Epon® 872 from Shell Chemical Company), having anepoxy equivalent weight of 650 to 750 and kinematic viscosity of 15 to25 poises at 25° C. is mixed with 80 parts of talc (Mistron Vapor®),forming the first mixture. A second mixture is prepared by combining 38parts of semisolid polyamide resin having an amine value of 90 and aviscosity of 10 poises at 150° C. (Versamid® 100) with 38 parts of asemisolid polyamide resin having an amine value of 238 and a viscosityof 35 poises at 75° C. (Versamid® 115) and 38 parts of talc (MistronVapor®).

These two mixtures are formed into slugs and extruded through aco-extrusion die so that the bands formed from the material are laiddown in side-by-side relation. As the bands of each material are laiddown in side-by-side relation, a tape is formed which is rolled to anyconvenient length and packaged as any conventional tape. This tape isutilized in the same manner as the tape of Example 1; however, it curesmore rapidly.

EXAMPLE 3

Following the procedure and utilizing the apparatus described in Example1, two separate mixtures are prepared as follows:

27 parts of a liquid epoxy resin having an epoxy equivalent weight of185 to 196 and a viscosity of 120 to 160 poises at 25° C. (Araldite®6010 of Ciba), and 19 parts of a solid epoxy resin having an epoxyequivalent weight of 385 to 500 and a melting point of 60 to 75° C.(Araldite® 6060) are mixed and blended together forming a uniformmixture. 40 parts of powdered alumina and 14.5 parts of short fiberasbestos such as Canadian asbestos 7R10 of the Phillip Carey Company aremixed forming a uniform putty-like material.

A second mixture is prepared by combining 57 parts of a semisolidpolyamide resin having an amine value of 90 and a viscosity of 10 poisesat 150° F. (Versamid ® 100), with 19 parts of asbestos fiber in a sigmablade mixer heated to a temperature of 180° F. After a uniform mixtureis obtained, no further heating of the mixture occurs, and 8 parts ofpowdered talc (Mistron Vapor®), is added with continuous mixing. 16parts of titanium dioxide powder (Zopaque® R69 of SCM Corporation), isdispersed in this mixture and blended until a uniform mixture is formed.The two mixtures are then extruded through a co-extrusion die and laiddown in side-by-side relation on release paper in the manner describedin Example 1 above. This tape has the properties and is utilized in thesame manner as the tape of Example 1.

Having thus described the invention, what is claimed is:
 1. An epoxytape comprising a first band of of an uncured epoxy resin compositionand a second band, said bands being joined in close side-by-siderelation throughout their entire length, said second band comprising acomposition capable of curing of said epoxy resin in said tape when saidfirst and second bands are combined to form a substantially uniformmixture .Iadd.whereby said tape may be mixed by kneading and may becured at ambient temperature, at elevated tempertures, and under waterand remains in a stable uncured state in absence of kneading.Iaddend..2. An epoxy tape according to claim 1 wherein said epoxy resin has anepoxy equivalent weight of about 650 to 750 and a kinematic viscosity of15 to 25 poises at 25° C. and said curing agent for said epoxy resin isa blend of polyamide resins having an amine value of 90 to 375 and aviscosity of 5 to 80 poises at 150° C.
 3. An epoxy tape according toclaim 2 wherein said epoxy resin is a blend of a solid epoxy resin witha liquid epoxy resin said blend having a kinematic viscosity of 0.01 to10 poises at 25° C.
 4. An epoxy tape according to claim 2 wherein saidepoxy resin and said polyamide resin are admixed with fillers andcolorants selected from the group consisting of talc, alumina, asbestosfiber, titanium dioxide, carbon black and mixtures thereof forming anextrudable composition.
 5. An epoxy tape according to claim 4 whereinsaid epoxy tape also includes about 30% to 40%, by weight, based on theweight of said tape of an electrically conductive substance selectedfrom the group consisting of electrically conductive carbon black andsilver powder. .Iadd.
 6. A kneadable epoxy tape according to claim 1wherein said first and second bands are of different color and visuallydistinct one from the other, so that substantially complete mixing ofthe material of one band with that of the other to form a substantiallyuniform mixture can be detected visually by formation of a substantiallyuniform color. .Iaddend.
 7. A kneadable epoxy tape according to claim 1wherein said first and second bands are self supporting andcharacterized in that substantially equal portions of said first andsecond bands can be removed from the tape and kneaded together forming acurable epoxy resin product. .Iadd.
 8. A kneadable epoxy tape accordingto claim 1 wherein said first and second bands remain in a stable anduncured state in absence of removing portions of said bands from theepoxy tape and kneading said removed portions of said bands to form acurable epoxy resin product. .Iaddend..Iadd.
 9. A kneadable epoxy tapeaccording to claim 1 wherein said second band contains a sufficientamount of curing agent to crosslink about 70 to about 150 percent of theavailable crosslinking sites in the epoxy resin in said first band ofthe epoxy tape. .Iaddend..Iadd.
 10. A kneadable epoxy tape according toclaim wherein said first and second bands are simultaneously extruded inside-by-side relationship. .Iaddend.